Three-way switching systems enable controlling electrical loads such as lighting loads from multiple control locations. These three-way switching systems include three-way switches that, for example, are wired to a building's alternating-current (AC) wiring system, are subjected to AC source voltage, and/or carry full load current as opposed to low-voltage switch systems that operate at low voltage and low current and communicate digital commands (e.g., usually low-voltage logic levels) to a remote controller that controls the level of AC power delivered to the load in response to the commands. As such, the “three-way switch” or “three-way system” include switches and systems that are subjected to the AC source voltage and carry the full load current.
Additionally, three-way switching system includes two three-way switches for controlling a single load where each switch is fully operable to independently control the load irrespective of the status of the other switch. In such a system, one three-way switch is typically wired at the AC source side of the system (e.g., at or on “line side”), and the other three-way switch is typically wired at the load side of the system. For example, FIG. 1 shows a standard three-way switch system 100 that includes two three-way switches 102, 104. The two three-way switches 102, 104 are connected between an AC power source 106 and a lighting load 108. When the three-way switches 102, 104 are both in position A or both in position B, the electrical circuit is complete and the lighting load 108 is energized. When one three-way switch 102 is in position A and the other three-way switch 104 is in position B or vice versa, the electrical circuit is not complete and the lighting load 108 is off.
Three-way dimmer switches can also replace three-way switches. For example, FIG. 2 depicts a simplified diagram of an example of a three-way dimming system 200 that includes a three-way dimmer switch 202 and a standard three-way switch 104. As shown in FIG. 2, the three-way dimmer switch 202 includes a dimmer circuit 210 and a three-way switch 212. The dimmer circuit 210 typically includes a bidirectional semiconductor switch such as a triac for regulating the amount of energy supplied to the lighting load 108. Specifically, the dimmer circuit 210 conducts load current to the lighting load 108 for some portion of each half-cycle of the AC waveform and does not conduct the load current to the load for the remainder of the half-cycle. Because the dimmer switch 202 is in series with the lighting load 108, the longer the dimmer switch conducts the load current, the more energy will be delivered to the lighting load 108. When the lighting load 108 is a lamp, the more energy delivered to the lighting load 108, the greater the light intensity level of the lamp. In a typical dimming scenario, a user may adjust a control of a user interface of the dimmer switch 202 to set the light intensity level of the lamp to a desired light intensity level. The portion of each half-cycle for which the dimmer switch 202 conducts is based on the selected light intensity level. As shown in FIG. 2, today, the three-way dimming system 200 includes one three-way dimmer switch 202, which can be located on either the line side or the load side of the system as, currently, two dimmer circuits such as the dimmer switch 202 can not be wired in series.
Additionally, three-way dimming systems such as the three-way dimming system 200 shown in FIG. 2 can employ a “smart” dimmer switch and/or a specially designed auxiliary (e.g., remote) switch that permits the dimming level to be adjusted from multiple locations. A smart dimmer is a dimmer that includes a microcontroller or other processing components for enabling an advanced set of control features and feedback options to the end user. To power the microcontroller, smart dimmers include power supplies that draw a small amount of leakage current through the lighting load each half-cycle when the bidirectional semiconductor switch of the dimmer circuit 210 shown in FIG. 2 is non-conductive. The power supply uses this small amount of current to charge a capacitor and develop a direct-current (DC) voltage to power the microcontroller. No load current flows through the dimmer circuit 210 shown in FIG. 2 of the three-way dimmer switch 202 when the circuit between the AC power source 106 and the lighting load 108 is broken by either three-way switch 212, 104. As such, currently, the dimmer switch 202 can not include a power supply and a microcontroller and still operate to properly provide the advanced set of features to the end user when the lighting load 108 is on and off.
To provide such a “smart” dimmer system, multiple lighting controls can also be used. FIG. 3 shows an example multiple location lighting control system 300 that can provide such a “smart” dimmer system. As shown in FIG. 3, the multiple location lighting control system 300 includes a wall-mountable smart dimmer switch 302 and a wall-mountable remote switch 304 (e.g., an accessory control). The dimmer switch 302 has a hot terminal H for receipt of the AC source voltage provided by the AC power supply 106, and a dimmed-hot terminal DH for providing the dimmed-hot voltage to the lighting load 108. The accessory control 304 is connected in series with the dimmed-hot terminal DH of the dimmer switch 302 and the lighting load 108 such that the accessory control 304 passes the dimmed-hot voltage through to the lighting load. The multiple location lighting control system 300 is described in greater detail in commonly-assigned U.S. Pat. No. 5,248,919, issued on Sep. 28, 1993, entitled LIGHTING CONTROL DEVICE, and U.S. Pat. No. 5,798,581, issued Aug. 25, 1998, entitled LOCATION INDEPENDENT DIMMER SWITCH FOR USE IN MULTIPLE LOCATION SWITCH SYSTEM, AND SWITCH SYSTEM EMPLOYING SAME, the entire disclosure of which is hereby incorporated by reference.
Additionally, the dimmer switch 302 and the accessory control 304 both have actuators to enable toggling the lighting load 108 on and off and/or for raising and lowering the intensity of the lighting load. The dimmer switch 302 is responsive to actuation or selection of the actuators to turn the lighting load 108 on or off or adjust the intensity level of the lighting load from a minimum intensity (e.g., approximately 0%) to a maximum intensity (e.g., approximately 100%). In addition, the dimmer switch 302 may control the intensity of the lighting load 108 to a preset intensity between the minimum and maximum intensities. When turning the lighting load 108 on and/or off, the dimmer switch 302 is operable to fade the intensity of the lighting load by increasing or decreasing the intensity of the lighting load from the minimum intensity to the preset intensity (e.g., or from the present intensity to the minimum intensity) over a predetermined amount of time (i.e., at a fade rate). The dimmer switch 302 uses a slow turn-off time (e.g., approximately 2.5 sec) to gradually turn off the lighting load 108, which provides an aesthetically pleasing reduction in the intensity of the lighting load and provides the user with a few seconds to exit the room in which the lighting load is located before the lighting load is completely off. The smart dimmer switch 302 can also include a linear array of visual indicators (not shown) that are illuminated to provide feedback of the intensity of the lighting load 108.
Actuation or selection of one of the actuators at the accessory control 304 causes an AC control signal, or a partially-rectified AC control signal, to be communicated from that accessory control to the dimmer switch 302 over the wiring between the accessory-dimmer terminal AD of the accessory control and the accessory-dimmer terminal AD of the dimmer switch. The actuators of the accessory control 304 contact momentary tactile switches inside the accessory control, such that the dimmer switch 302 receives short pulse signals from the accessory control (e.g., 100-200 milliseconds in length) representing a closure of one of the momentary switches in accessory control. The dimmer switch 302 is responsive to the control signal to alter the dimming level or toggle the lighting load 108 on and off. Thus, the lighting load 108 can be fully controlled from the accessory control 304.
Although the multiple location lighting control system 300 shown in FIG. 3 enables the use of a smart dimmer switch in a three-way system, a customer may need to purchase the accessory control 304 along with the smart dimmer switch 302. Often, the typical customer is unaware that an accessory control is used or needed when buying a smart dimmer switch for a three-way system until after the time of purchase when the smart dimmer switch is installed and it is discovered that the smart dimmer will not work properly with the existing three-way switch.
Additionally, to provide a “smart” dimmer system, a “smart” three-way dimmer switch may be used with a typical or standard three-way switch. FIG. 4 illustrate a diagram of a example three-way dimming system 400 that includes a smart three-way dimmer switch 402 that is operable to work with a standard maintained three-way switch 404. Thus, there is no need for the installer to purchase a unique accessory control to replace the three-way switch 404. The smart three-way dimmer switch 402 is wired in place of a previously installed switch or dimmer switch (e.g., the three-way switch 102 shown in FIG. 1 or the dimmer switch 202 shown in FIG. 2). To provide such a system, a simple rewiring 410 can be carried out in the wallbox of the three-way switch 404 to disconnect the dimmed-hot terminal DH of the smart three-way dimmer switch 402 from the first switch position of the three-way switch 404 (i.e., position A in FIG. 4) and to connect the dimmed-hot terminal DH to the lighting load 108. The other switch position of the three-way switch 404 (i.e., position B in FIG. 4) is connected to the accessory-dimmer terminal AD of the smart three-way dimmer switch 402.
As such, the smart three-way dimmer switch 402 shown in FIG. 4 is connected between the AC power source 106 and the lighting load 108 independent of the position of three-way switch 404. The three-way switch 404 now operates by either connecting the dimmed-hot voltage to or disconnecting the dimmed-hot voltage from the accessory-dimmer terminal AD on the smart three-way dimmer switch. The smart three-way dimmer switch 402 can also be wired to the load side of system 400 and operation of the three-way switch 404 would connect and disconnect the AC power source voltage to and from the accessory-dimmer terminal AD on the smart three-way dimmer switch. Also, a two-way switch an be used in place of three-way switch 404 since the first position A is not being used. Rather than receiving a signal at the accessory-dimmer terminal AD that is a short pulse (i.e., representing a closure of one of the momentary switches in the accessory control 304), the smart three-way dimmer switch 402 determines when the voltage at the accessory-dimmer terminal AD changes states (i.e., from an AC line voltage signal to zero volts, and vice versa). Based on this determination, the smart three-way dimmer switch 402 toggles the state of the lighting load 108. The three-way dimming system 400 of FIG. 4 is described in greater detail in commonly-assigned U.S. Pat. No. 7,247,999, issued Jul. 24, 2007, entitled DIMMER FOR USE WITH A THREE-WAY SWITCH, the entire disclosure of which is hereby incorporated by reference.
The dimmer switch 402 of the three-way dimmer system 400 shown in FIG. 4 may use a the slow turn-off fade rate (i.e., approximately 2.5 seconds) to gradually turn off the lighting load. While this gradual adjustment of the intensity of the lighting load 108 provides benefits to the user as previously mentioned, the reduction may not be immediately perceptible by the human eye. A user of the smart dimmer switch 302 or the accessory control 304 of the lighting control system 300 shown in FIG. 3 may be aware of the slow turn-off rate provided by the smart dimmer switch. Unfortunately, the user of the standard three-way switch 404 of the dimming system 400 may expect the intensity of the lighting load 108 to change rapidly when the lighting load is turned off. Since the dimmer switch 402 uses the slow turn-off or turn-on fade rate, the adjustment of the intensity of the lighting load 108 in response to an actuation of the three-way switch typically is not immediately noticed by the user. As such, the user can become confused causing the user to once again actuate the three-way switch 404 and, thus, change the intensity to an undesired level and/or even conclude that the three-way switch is not functioning correctly.